In two different studies, US scientists have succeeded in creating the stem cells which produce blood.
Both studies – published in Nature – are concerned with making haematopoietic stem cells (HSCs), which are found inside the bone marrow and can divide to generate each of the many types of blood cell.
In the first study, a team at the Daley laboratory at Boston Children’s Hospital, Massachusetts, took human embryonic stem cells or induced pluripotent stem cells (iPSCs). They exposed these cells to developmental chemicals called cytokines, and also identified seven transcription factor genes associated with HSCs and introduced them into these stem cells using a viral vector. The resulting cells were not identical to natural HSCs, but appeared to perform the same function: mice injected into the leg bone with the cells, subsequently developed human blood cells of various types in the bone marrow and circulation.
In the second study, the team led by scientists at Weill Cornell Medical College in New York bypassed the iPSCs stage entirely. They isolated cells from the blood vessel lining of adult mice and inserted four transcription factor genes, again using a virus. They grew these cells on material derived from the human umbilical cord which provided factors to guide development into HSCs.
Again, the cells produced – once transplanted into mouse recipients – were able to produce mature blood cells, including in mice which were genetically modified to lack an immune system.
Generating replacement HSCs from a patient's own cells, through either method, could allow a therapy to be tailored to an individual. Dr Ryohichi Sugimura at the Daley Lab, a lead author of the first paper, said: 'This step opens up an opportunity to take cells from patients with genetic blood disorders, use gene editing to correct their genetic defect and make functional blood cells. This also gives us the potential to have a limitless supply of blood stem cells and blood by taking cells from universal donors. This could potentially augment the blood supply for patients who need transfusions.'
An article in Nature, co-written by Dr Carolina Guibentif at the Wellcome Trust and MRC Cambridge Stem Cell Institute in Cambridge, discussed the findings, referring to the production of HSCs in the laboratory as a 'long-sought goal of stem-cell biology'. Dr Guibentif, who was not involved in either study, told The Independent: 'People have been trying to do this for 20 years unsuccessfully. This is the first time… they have got cells that can self-renew and give rise to all sorts of blood cells, so of course it’s a big step towards the goal, but we are not quite there yet.'
But she also cautioned that such generated cells could be a cancer risk: 'Many of the transcription factors used in the current studies have also been implicated in the initiation of leukaemia.'